Ge quantum-dot polysilicon emitter heterojunction phototransistors for 1.31–1.55 μm light detection

✍ Scribed by Rongshan Wei; Ning Deng; Hao Dong; Min Ren; Lei Zhang; Peiyi Chen; Litian Liu

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 443 KB
• Volume: 147
• Category: Article
• ISSN: 0921-5107
• DOI: 10.1016/j.mseb.2007.08.005

✦ Synopsis

A Si/SiGe HBT-type phototransistor with 10 Ge-dot layers (8ML in each layer, separated by 30 nm Si spacer) incorporated in the base-collector junction was grown by UHV-CVD. To achieve low dark current density and high photo-responsivity, a high-low emitter profile consisting of a heavily doped polysilicon contact on top of a thin epitaxial emitter cap has been fabricated. At room temperature, I-V measurement showed a low dark current density of 3 × 10 -5 A/cm 2 at 3 V. The measured breakdown voltage BV ceo was about 12 V. A photo-responsivity of 1.94 and 0.028 mA/W was achieved at 1.31 and 1.55 m for normal incidence, respectively. Compared to a p-i-n reference detector with the same quantum-dot layer, the responsivity is improved by a factor of 45 and 20 at 1.31 and 1.55 m, respectively.